In a radio communication, data is transmitted in units of a certain time frame called a “radio frame.” When a series of data is transmitted, the smaller the proportion of continuous errors (burst errors) in the transmission time of this data, the higher accuracy in error correction can be obtained on the receiving side. Therefore, this data maybe mapped to a plurality of radio frames and transmitted. In the 3GPP (3rd Generation Partnership Project) specification in particular, 1, 2, 4 or 8 radio frames are used according to the types and number of data pieces to send a series of data pieces.
When a plurality of types of data is transmitted simultaneously, data pieces to be mapped to the same radio frame are combined and a string of combined data pieces is mapped to the radio frame. Here, the data pieces to be transmitted simultaneously are not always transmitted with the same number of radio frames. That is, when for example, two kinds of data are transmitted, one type of data may be transmitted with two radio frames and the other type of data may be transmitted with four radio frames.
The data on the radio frames transmitted as described above is demodulated frame by frame at a reception apparatus and when a plurality of data pieces is combined, the data is divided into their respective data pieces and stored in a storage apparatus such as a memory for each data. When received data is the one sent with one frame, a series of data pieces has been received when one frame of data is received, and therefore the data stored in the storage apparatus is read at this point in time and subsequent processing such as frame combination and forward error correction is carried out. On the other hand, when received data is the one sent with a plurality of frames, a series of data pieces has not been received yet when one frame of data is received, and therefore data pieces to be received with subsequent radio frames are stored one by one in the storage apparatus. Then, after all radio frames including the series of data pieces is received, the data stored in the storage apparatus is read and subjected to subsequent processing such as frame combination and forward error correction.
In this process, there are various methods of securing storage areas to store the received data pieces in a storage apparatus such as a method of securing storage areas for the received data pieces in the order in which they are received or a method of securing storage areas corresponding in number to radio frames including their respective data pieces.
However, in the case of the method of securing storage areas for received data pieces for each radio frame in the order in which they are received, a series of data pieces spanning a plurality of frames is stored separately for every frame and at the same time a complete series of data is read from the storage apparatus for subsequent processing and the area where the relevant data was stored becomes a free space, which causes the area used in the storage apparatus to become thinned out, resulting in a problem that the required storage capacity increases.
Furthermore, in the case of the method of securing storage areas corresponding in number to radio frames including the relevant data pieces, when there is a plurality of data pieces spanning a plurality of radio frames, the area used in the storage apparatus may become thinned out as in the above described case resulting in a problem that the required storage capacity increases.
Specific examples of these problems will be explained with reference to FIGS. 1 to 3 below.
FIG. 1 illustrates a configuration example of radio frames that transmit a plurality of data pieces. As shown in the figure, data pieces A to J are transmitted with radio frames #1 to #4 and the radio frame #1 transmits the parts corresponding to the 1st frames of the data pieces A to D. Furthermore, the radio frame #2 transmits the part corresponding to the 1st frame of the data piece E and the parts corresponding to the 2nd frames of the data pieces B and C. In the like manner, the radio frames #3 and #4 transmit their respective data pieces. In the case of the data pieces A, D, E, F, I and J, one frame carries their complete set of data, while in the case of the data pieces B, G and H, two frames carry their complete set of data and in the case of the data piece C, four frames carry a complete series of data.
When storage areas are secured for the data pieces transmitted in this way in the order in which they are received, the state of the areas used is as shown in FIG. 2. As shown in FIG. 2, with the radio frame #1 the storage areas are secured for the parts corresponding to the 1st frames of the data pieces A to D which are stored one by one. The data pieces A and D which have their complete set of data with only the radio frame #1 are read for the subsequent processing and the areas of the data pieces A and D are released. In the case of the radio frame #2, storage areas are secured for the part corresponding to the 1st frame of the data piece E and parts corresponding to the 2nd frames of the data pieces B and C, which are stored one by one. At this time, the part in which the data piece A was stored was released and remains free, but since the amount of data of the parts corresponding to the 2nd frames of the data pieces B and C and the amount of data of the part corresponding to the 1st frame of the data piece E are greater than the data piece A, it is not possible to store the parts of the data pieces B, C and E using only this free space. Furthermore, if the parts of the data pieces B, C and E are divided and the above described free space is used for them, controlling these storage areas would be very complicated.
Likewise, storage areas are secured for the respective data pieces in the order in which they are received and the data pieces are stored. Here, for example, when the data included in the radio frame #3 is stored, the data C is stored in different pieces away from one another though they constitute a series of data pieces. Because of this, the processing when outputting a series of data pieces for subsequent processing becomes complicated. Furthermore, when even the data included in the radio frame #4 is stored, the areas used are thinned out, which prevents effective use of storage areas and increases the required storage capacity.
Furthermore, the state of the areas used when storage areas corresponding in number to the radio frames including the respective data pieces shown in FIG. 1 are secured and the data pieces are stored is as shown in FIG. 3. As shown in FIG. 3, in the case of the radio frame #1 , storage areas are secured for the data pieces A to D according to the number of radio frames that include these data pieces, and these data pieces are then stored. That is, storage areas corresponding to one frame for the data pieces A and D, two frames for the data piece B and four frames for the data piece C are secured. The data pieces A and D which have their complete set of data with only the radio frame #1 are read for the subsequent processing and the areas for the data pieces A and D are released. In the case of the radio frame #2, the parts corresponding to the 2nd frames of the data pieces B and C are stored in the secured areas and for the data piece E, a storage area corresponding to one frame is secured and the data piece E is stored there. At this time, the part in which the data piece A was stored was released and remains free, but since the amount of data of the part corresponding to the 1st frame of the data piece E is greater than the data piece A, it is not possible to use this free space.
Then, storage areas are secured for all the relevant data pieces when the start frame of each data piece is stored in the like manner. In this case, too, when, for example, data pieces up to the ones included in the radio frame #4 are stored, the areas used remain thinned-out, which prevents effective use of storage areas and increases the required storage capacity.